This invention relates to energy recovery and, more particularly, this invention relates to a method and apparatus for recovering otherwise lost energy from a compressor and prime mover.
Gas compressors such as air compressors are well-known in the art and are widely used in the construction industry. Such air compressors are typically driven by a Diesel engine, although compressors can also be driven by a gasoline engine, a gas turbine or from a Rankine cycle prime mover. For ease of discussion, the following description will refer to the Diesel engine in an exemplary manner, although it is to be distinctly understood that "prime mover" as used in this specification and the claims is meant to include any form of prime mover such as the Diesel engine, gasoline engine, gas turbine, Rankine cycle prime mover, or any other energy source.
A Diesel engine driving a compressor converts only one third of the heat content of the fuel being burned to useful energy, that is, power for driving the load. Of the remaining two-thirds, one third is converted to heat which is normally carried away in the engine cooling medium, usually water or air. The remaining third is converted to heat which is normally carried away in the engine exhaust gas. Thus, two-thirds of the potential recoverable energy is automatically lost as heat.
Then, of the energy transmitted to the compressor, all of the power delivered by the engine is converted back into heat. Specifically, all the shaft horsepower input to the compressor is converted to heat in one of six forms, namely, heat radiated from the frame, cylinders, coolers, and piping to the atmosphere; heat conducted from the frame to the foundation; heat carried from bearings by lubricating and cooling oil and radiated to the atmosphere or transferred to the cooling medium, such as water or air, for disposal; heat carried away by the cooling medium in the cylinder jackets; heat carried away by the cooling medium in intercoolers; and heat carried out of the compressor in the compressed gas as it leaves the system.
Thus, upon consideration of these factors, it becomes apparent that all the power for driving the compressor is converted back to heat and there is a startling opportunity for power recovery and feedback from all three thirds of the heat content of the fuel being burned. Recovery and use of heat from a prime mover has been accomplished in the prior art, but this has not been accomplished with a compressor in combination with a prime mover. Considering the present scarcity of fossil fuel and the projected critical scarcity in the foreseeable future, there is a glaring need for means to recover at least a portion of this wasted energy.